1. Field of the Invention
The present invention relates to vehicles equipped with rotary piston engines. More particularly, the present invention pertains to tractive power transmitting mechanisms for vehicles having rotary piston engines.
2. Description of Prior Art
In motor vehicles of the front-engine, front-wheel-drive type or of the four-wheel drive type, a differential gear unit is required in the front axle. Conventional motor vehicles have such front differential gear units mounted through resilient rubber mounts on front frames of the vehicle bodies as taught, for example, by Japanese utility model disclosure No. 56-62226. The utility model does not describe the location of the front differential gear unit with respect to the engine. However, in order that the engine be supported as low as possible as usually required in passenger vehicles, it has also been proposed to locate the front differential gear unit at one side of the engine. In the case of a vehicle having a rotary piston engine, however, if the front differential gear unit is located at one side of the engine, a problem will be encountered in the arrangements of shafts for transmitting the engine power from the transmission unit to the front differential gear unit. A rotary piston engine generally has a transverse width greater than that of a reciprocating piston engine so that the propeller shaft between the transmission unit and the front differential gear unit has to be inclined with respect to the longitudinal axis at an angle greater than that in a vehicle having a reciprocating piston engine. As a result, rotation cannot be transmitted smoothly to and from the propeller shaft, and the universal joints at the opposite ends of the propeller shaft may possibly be overloaded.
It may be possible to mount the front differential gear unit directly on the engine casing so that the inclination angle of the propeller shaft can be decreased. However, such an arrangement is not recommendable because there will be a possibility of interference with various engine components, such as intake and exhaust manifolds, ignition plugs and other engine accessories. It should further be noted that a rotary engine includes a casing comprised of a plurality of housings which are connected together by means of connecting bolts and, if the front differential gear unit is mounted on one of the housings, the reaction force on the casing of the front differential gear unit may apply to the housing on which the gear unit is mounted a force which tends to separate the subject housing, from the adjacent housing weakening the seal between these housings.